Hot Rod Forum banner

Carb

709 12
Got a stock 454 or close to stock Needs a carb. Would a 750 Holly with manual secondary be ok Or is it to big. Don’t want nothing to big.
1 - 3 of 3 Posts

· Registered
Joined
·
5,082 Posts
Using a double pumper carburetor from Holley or Holley style carburetor will need some requirements vs a vacuum secondary Holley in order for it to operate correctly on the secondary side opening. A double pumper needs quick rpms and a vehicle that is light and not something heavy that takes a bit to get going as a double pumper when hitting the throttle and you end up opening up the secondary side of things, without quick enough rpms to get the vehicle moving it will be a big bog and a real soggy signal catching up with the load on the engine.

They can work with vehicles that can get rpms up quickly in the rpm band of its said build and camshaft rpm range and also if setup correctly. It can be used on automatic transmissions and does not need some high 3000 plus stall convertor like Holley recommends as I have used them many times on a th350 using just a 2200 stall convertor and 3.42 rear gearing. The success is my truck could hit the rpms very quickly and pick up speed without any lugging.

A vacuum secondary Holley like mentioned would be the better choice as it can be made to open up to demand as it goes by air velocity as does a Qjet carburetor. The Quick fuel brawler 750 carbs would be a good investment if you want to go that route and they have an adjustable vacuum secondary pod that you can control the rate it opens up. With a double pumper if its not sized or tuned correctly its not very forgiving. With you having a big block a 750 would be more then enough for it but the style depends on the setup such as your rear gearing and the vehicle weight and how quick it gets up to speed and other factors.

You don't want to end up with a band aid tune on the double pumper with a 50cc secondary pump shot size to cure a massive bog because its not the best choice for your vehicle. I have seen many times folks can't get one properly tuned because its not the right carb choice for there ride and end up with band aid type of a tune such as a big 50cc pump shot on either the front and rear both on the pump shot circuit. A Qjet will give better mileage and overall better results as far as being the best fuel metering but a Holley will give more performance if a more performance oriented build.
 

· Registered
Joined
·
5,082 Posts
All I meant was folks who put a double pumper on a vehicle that was not equipped for one, because of the way the secondaries would open so fast hitting wide open throttle and in order to cure a massive bog because of the secondary side opening up to fast and no way of adjusting it in relation to demand from the engine, folks have used a bigger pump 50 cc shot because the normal 30cc size and shooter size and pump cam combo would not be enough to cure the bog coming from the opening of the secondary and sometimes with the combination of the front coming into play so fast at wide open throttle.

A 50cc is going to give more fuel over a set amount of throttle travel vs a 30cc. Just saying putting a double pumper on a vehicle that can't take it will end up with a band aid tune job at times if its too big and not size correctly and put on a build that is not equipped for one. Have seen it and read about it many times. Not saying that is always the case but they are not just able to be thrown on any engine and work just fine. Holley double pumpers will open up fast when hitting the throttle regardless of the vehicle its put on. That is why many who have put them on builds that they should have not been stuck on the first place always have complained of horrible bogs and end up with a way out of proper setup with the pump shot on them. Just an example on what I stated.
 

· Registered
Joined
·
5,082 Posts
I second what Bogie said. I always forget about the Edelbrock AVS2 series of carburetors and if running something stock it would be good and easy to tune and more efficient then a Holley style. If your willing to run something different but if you want to run a Holley I recommend a 750 vacuum secondary Quick fuel brawler as it will have more tuning features and adjustments vs a Holley brand equal and tune for your build.

All depends on your preference. The AVS2 would give the best mileage and be good for cruising. Listed below is a Quick fuel 770 (750cfm) brawler which is a 4150 since it has a secondary metering block and the 750 Quick fuel slayer which is a 4160 since it has no secondary metering block but it has secondary jets but you can't change anything on the idle circuit wise on the metering plate. Then the Edelbrock AVS 2 800 and 650.






 
1 - 3 of 3 Posts
Top